Extent Of Infestation Research Articles

The human impact of colonization and parasite infestation in subtropical lowlands of Bolivia

The effect of colonization on the infestation by intestinal parasites was examined in the subtropical lowlands of Bolivia. High frequency of parasite carriers indicates the close parasite-human relationship in this area. But the variation in the extent of infestation among colonies shows the modification of this relationship by the development of cultivation and/or adjustment for living facilities which were influenced by differential colonizing processes in terms of the time elapsing since initial settlement, the type of colonization and the origin of the colonists.

EPIBIOTIC MICROBIAL INFESTATIONS OF CULTURED CRUSTACEANS1

ABSTRACTMicrobial epibionts have continually hampered efforts to rear crustaceans. Although a variety of microbial agents may be responsible for mortalities on a variety of crustaceans, several characteristics are sufficiently similar to consider epibiotic microbial fouling as a single syndrome. Epibionts use the surface of the animal only as a substrate and rely on dissolved nutrients in the seawater for nourishment. The type and extent of infestation corresponds to water quality. Lethality is presumed to result from asphyxia caused by occlusion of respiratory surfaces. The easily diagnosed filamentous epibionts may only signify advanced stages of the disease while non‐filamentous forms are more directly related to mortalities. Filamentous and non‐filamentous forms also respond differently to therapeutic treatment. Infestation and mortality in egg masses of crabs occur most heavily on the external portions of the egg mass and decline exponentially with increased depth into the egg mass. Temporal progression occurs in the same manner. Some evidence suggests that the exterior layers “seed” the successive internal eggs with epibionts. Various observations have prompted speculation concerning the susceptibility of crustaceans to microbial epibionts in relation to their culture environment. Potential methods of prevention and treatments are discussed.

Notes on the role of ticks feeding on lagomorphs and ingestion of ticks by vertebrates in the epidemiology of Rocky Mountain spotted fever.

Sonenshine & Clifford (1973, J. Med. Ent. 10 : 497–502) reported on the incidence of rickettsiae of Rocky Mountain Spotted Fever (RMSF) in birds in Virginia, and on the extent of infestation of these birds with immature Haemaphysalis leporispalustris (Packard). McKiel (unpubl.) obtained similar data for SW Nova Scotia, and Martell, Yescott & Dodds (1969, Can. J. Zool. 47 : 183–84) reported on some infestations of birds in Nova Scotia. All stages of H. leporispalustris occur abundantly on lagomorphs (e.g., Sylvilagus and Lepus ) in North America, but there continue to be questions about links between the bird- Haemaphysalis -Iagomorph cycle and the rodent- Dermacentor -larger mammal (including man) cycle of RMSF. Sonenshine & Clifford (1973, loc. cit.) found very few Dermacentor variabilis (Say) on Sylvilagus in Virginia, and they stated “the data do appear to raise doubts as to its (i.e., involvement of ticks on birds in spreading RMSF to ticks that infect man) importance and suggest the need for further study and evaluation.” This note (1) presents new data on the infestation of hares with both Dermacentor and H. leporispalustris in Nova Scotia and (2) draws attention to the plausibility of another link between the cycles, that of ingestion of ticks by vertebrates.

DISTRIBUTION OF SETARIA VIRIDIS IN WESTERN CANADA

Setaria viridis (L.) Beauv. (green foxtail) was present in 84, 32, and 28% of the 406 fields surveyed in Manitoba, Saskatchewan, and Alberta, respectively. In Alberta and Saskatchewan, S. viridis occurred more frequently on moderately coarse- to coarse-textured soils than on finer soils. Densities and the extent of infestation in each field was greater on coarse-textured soils than on fine-textured soils in these two provinces. However, in Manitoba, the presence of this species was not related to soil texture, since the frequency of occurrence in fields, the extent to which each field was infested, and the maximum densities recorded in each infestation were uniformly high for all soil textural groups. In Manitoba, 43% of the infestations included densities of 1000 or more plants per m2 and the highest density recorded was 10,000/m2. This weed is more widespread than was reported in previous surveys and infests nearly 28% of the cultivated acreage in Western Canada. In laboratory tests, emergence was similar in clay, loam, or sandy loam soils kept at field capacity or at higher moisture levels within a temperature range of 10–24 C. Emergence was reduced by planting at depths below 5 or 7.6 cm, depending upon soil moisture. Germination increased with temperature, and it is suggested that coarse-textured soils are invaded most readily because they warm up faster than fine-textured soils. Cropping practices may also affect distribution since the buildup of S. viridis is believed to be checked by summer-fallowing. The frequency of summer-fallowing in Manitoba is lower than in Saskatchewan. This may account for the high populations of S. viridis in Manitoba.

Nature and assessment of losses caused by sugarcane borers

On the two main types of sugarcane borers, viz. top and stalk borers, the latter are generally more harmful than the former. In the young crop stalk borers cause dead hearts, but at later stages their attack is normally restricted to the joints, except in (almost) mature cane when again many tops may be destroyed.In this paper emphasis is on assessing the extent of infestation and the relationship between stalk borer injury and loss of sugar. Various criteria and methods are compared. It is concluded that the ultimate loss in yield due to stalk borer infestation may be as large as 1% for each 1% joints bored, all forms of injury included.

Effect of the opaque-2 gene in maize ( Zea mays L.) on the extent of infestation by Sitophilus oryzae L.

Effect of the opaque-2 gene in maize ( Zea mays L.) on the extent of infestation by Sitophilus oryzae L.

SPREAD OF TOADFLAX IN SASKATCHEWAN

During 1949–57, surveys and resurveys were conducted throughout one-third of the settled area of Saskatchewan for the purpose of ascertaining the abundance of several species of introduced persistent perennial weeds and to evaluate their rates of increase. The methods used included an extensive farm-to-farm survey, sampling quarter-sections along transects in heavily infested areas, and resurveys of the same land at intervals. Detailed studies along line transects in various habitats were used during 1954–61 to obtain more precise data concerning increases and decreases in extent of infestations. These studies indicated that, within the area surveyed, 142,702 acres were infested with toadflax (Linaria vulgaris Mill.) in 4,993 quarter-sections. The increase in abundance of the weed was particularly great from 1949 to 1954, while after that date uncultivated infestations spread much less rapidly and cultivated ones were kept under fairly good control. The data indicate that the weed probably responds to weather conditions in such a way as to be favored relative to grasses by deficiency of soil moisture in the upper levels of the soil.

Tyroglyphid mites in stored products Methods for the study of population density

The known methods for detecting the presence of tyroglyphids are described. For coarse materials, such as seeds, sieving is recommended. For flour, it is better to examine exposed surfaces, or to keep samples in glass vessels and examine for the runnels made by mites against the glass. Methods of sampling to provide information about the density and extent of infestations are described. Samples must usually be treated in the laboratory. While methods which do not involve the separation of the mites from the material are referred to, such separation is usually necessary. Mites may be separated from most materials by the modified Berlese funnel method of Chernuishev and Petrova; means of overcoming certain disadvantages are suggested. However, vigorous sieving is recommended for coarse materials, and a flotation method, using dichlorethylene, for fine materials such as flour. It is usually more satisfactory to examine and count the mites than to estimate the numbers volumetrically or gravimetrically. They are counted in a dish containing oil, placed on squared paper under a low‐power microscope. A modification of this method, for dealing with large numbers, is described. Methods of expressing population density are briefly discussed.

The Numerical Determination of Trichomonas hominis in Urine and its Practical Implications in Genitourinary Parasitism.

Abstract 1.1. It is possible now to determine quantitatively the degree of urinary trichomoniasis by the use of the hemocytometer. The flagellates are counted as are cells in spinal fluid and the number per cubic millimeter of the sample examined is thus obtained. When the protozoan is too motile for accurate enumeration, two drops either of 0.25 per cent formalin or of 1 per cent formalin are added to 5 c.c. of the material. Centrifugalization without apparent injury to the trichomonads is possible, especially if formalin is used as indicated prior to this procedure. 2.2. The application of this method in vaginal trichomoniasis, as well as a modification of it outlined in the text for the numerical determination of these organisms in prostatic secretion, has been suggested. 3.3. The clinical significance of this procedure rests in the ability to estimate quantitatively the extent of infestation, its progression or decline, and the efficacy of therapy. 4.4. There is nothing in the morphologic and biologic characteristics of other flagellates, amebae and ciliates, if and when so encountered, that would prevent a satisfactory application of this method. 5.5. The great dilution of formalin which appears to be toxic to trichomonads suggests its possible use in therapy, both in the urinary and digestive tracts.

STUDIES ON OSCINELLA FRIT LINN.

Summary.Data, collected in Sweden during the year 1927, indicate the existence of considerable variation in extent of infestation of the grain of different varieties, sown at the same time. Also they suggest that sterility or “blindness” of grain may be a varietal character.

STUDIES ON OSCINELLA FRIT LINN: OBSERVATIONS ON INFESTATION AND YIELD, SUSCEPTIBILITY TO INFESTATION, RECOVERY POWER, THE INFLUENCE OF VARIETY ON THE RATE OF GROWTH OF THE PRIMARY SHOOT OF THE OAT AND THE REACTION TO MANURIAL TREATMENT

Summary.The notes collected in the present publication are each concerned with some aspect of the problem of production of varieties of oat plants resistant to the attack of the frit fly.The quality of a variety may compensate for comparatively heavy infestation.Data are recorded confirming previous experimentation relating to the susceptibility of the oat shoot to infestation, emphasising its limitation to the early leaf stages.Experimentation concerned with recovery power after injury showed that different varieties of oats react very differently and indicated the importance of the primary shoot in relation to yield. A few field data are recorded to support this inference.With common English varieties of oats the influence of variety on the rate of growth of the primary shoot was practically negligible, and therefore observed differences between varieties in extents of infestation of primary shoots cannot be ascribed to variations in rates of growth of primary shoots. The time of tillering did not depart markedly from the mean, but it was not correlated with time of shoot production, so that correlation between extent of infestation of shoot and of grain cannot be expected.Excess of nitrogenous manure failed to influence the extent of shoot infestation but effected a reduction in the extent of grain infestation during a season when the extent of the attack of the fly was below normal.

STUDIES ON OSCINELLA PRIT LINN.: SUPPLEMENTARY DATA ON THE RELATION BETWEEN VARIETAL DIFFERENCES OF OAT PLANTS AND SUSCEPTIBILITY TO INFESTATION

SUMMARYDuring the year 1924 additional data, in relation to varietal resistance to attack, were collected by repeating as nearly as possible the investigation conducted during the previous year, with the exception that only those varieties of oat were used, which were most (Goldfinder and New Abundance) and least resistant (Superb and Supreme).During the second season, during which, on the whole, conditions were unfavourable to damage by frit fly, varietal differences were again effective so far as stem infestation was concerned. The two varieties, Goldfinder and New Abundance, were significantly resistant as compared with the variety Supreme, similar differences being observed in the two seasons. Very late sowing indicated that varietal differences among very young plants were ineffective in influencing extent of infestation.Small significant differences were observed in relation to the grain infestation, but from the evidence available it would appear that constant values for these differences are unlikely to occur over a period of years, because extent of infestation is largely dependent on the history of the crop during the early growing period.

The Prevalence of Hookworm and Other Intestinal Nematodes in Adult Filipinos

During the collegiate year 1921-1922 students of the University of the Philippines at Los Bafios were examined for intestinal parasites in connection with medical examination that is required of all matriculants at the university. The object of the examinations for parasites was to determine primarily the incidence and degree of infestation of normal adult Filipinos with hookworms and, incidentally, to obtain information on the degree and extent of infestation of these individuals with other intestinal parasites. Studies on intestinal parasitism in the native population of the Philippine Islands are not novel undertakings. Since the American occupation of the Philippine archipelago a number of surveys have been made with a view to determining the incidence of protozoon and helminthic parasites in Filipinos and the bearing of such parasitism on public health. These surveys have been based, for the most part, on studies of inmates of Bilibid Prison, of patients in the Philippine General Hospital, on records of the medical departments of the army and navy and on records of autopsies performed in the College of Medicine and Surgery of the University of the Philippines. Several investigations on the prevalence of intestinal parasites in certain localities have also been published, but despite the fact that a considerable mass of data have been accumulated, no parasitological study based on the normal heterogenous adult population of the Philippines and carried out by modern methods has been published prior to this investigation. The fact that the student population of Los Bafios is typical of the population of the Philippine Islands in general was the chief reason why this study was undertaken. Forty-six provinces and subprovinces including the city of Manila are represented in this survey. The character of the student population at Los Bafios is quite varied, embracing various economic classes in proportions approximating the relative proportions of these classes in the the general insular population. The data obtained in the course of this investigation may be considered,